Don't forget Oasis isn't the one creating the ninjas, it's the Tencent - the one who owns the China server (the original server). The longer they do not add anymore canon characters, the longer they can milk whales. This is why you most likely haven't ninjas like night guy, kagura, or updates to the major story line.

They will keep on adding random characters like swimwear, suit, kimono, et*il they are getting tired of milking players.